The present invention relates generally to microstructure-bearing film surfaces. In particular, the present invention relates to apparatus having and methods of using layers of microstructured film surfaces as a reservoir for storing and dispensing liquid.
Microstructured film surfaces are used in a variety of products and processes. For example, U.S. Pat. Nos. 5,069,403 and 5,133,516 relate to microstructure-bearing film surfaces used to reduce drag resistance of a fluid flowing over a surface. In particular, conformable sheet material that employs a patterned first surface comprising a series of parallel peaks separated from one another by a series of parallel valleys is disclosed.
Also, microstructure-bearing film surfaces have been used to transport fluids. For example, U.S. Pat. Nos. 5,514,120 and 5,728,446 relate to absorbent articles, such as diapers, having a liquid management film that rapidly and uniformly transport liquid from a liquid permeable topsheet to an absorbent core. The liquid management film is a sheet, typically flexible, having at least one microstructure-bearing hydrophilic surface with a plurality of grooves or channels formed thereon.
Nevertheless, other new and useful applications of microstructured film surfaces are desired.
The present invention is based on the recognition that microstructured films having channels or grooves formed on a major surface of the film, when stacked, capped, and/or otherwise layered, can form an array of capillaries for containment and delivery of liquid. Liquid can be stored and subsequently dispensed, extracted, or otherwise removed from the reservoir in a number of ways. For example, the openings of the channels can be inserted into a liquid that is capable of wetting the film material so that capillary action will cause the liquid to move into the array of channels. When the openings of the channels are removed from the liquid, attractive forces between the liquid and the interior surfaces of the channels cause the liquid to remain in the channels so that the liquid is effectively contained within the array of channels. When a potential sufficient to overcome the attractive forces is applied to the openings of the channels, the liquid moves towards the openings and out of the channels so that the once-contained liquid is dispensed from the channels. The layers in which the channels are formed can be fabricated and stacked, capped, and/or otherwise layered in a linear, uniform manner to facilitate anisotropic (that is, directionally dependent) dispensing, extraction, or removal of liquid on demand in a controllable fashion.
Reservoirs of the present invention are efficient in that a high percentage of the liquid stored in the reservoir can ultimately be dispensed, extracted, or otherwise removed and are easily and economically manufactured from a variety of materials, including relatively inexpensive, flexible or rigid polymers. The structured surface features of the reservoir are highly controllable, predictable and ordered, and are formable with high reliability and repeatability using known microreplication or other techniques. The reservoirs can be produced in highly variable configurations to meet the storage and dispensing, extraction, or other removal requirements of a given application. This variability is manifested in such features as structured surface feature possibilities (for example, discrete or open channels), channel configurations (for example, wide, narrow, xe2x80x98Vxe2x80x99 shaped, rectangular, primary and/or secondary channels), stack configurations (for example, bonded or unbonded, facing layers, non-facing layers, added layers, aligned channels, offset channels, and/or channel patterns), and channel outlets (for example, size, configuration, or pattern). In addition, the layers may be treated to increase or decrease the wettability of the structured surface or for other purposes.
A reservoir according to the present invention includes at least one layer of microstructured film having a plurality of elongated channels formed on a structured surface of the microstructured film. The reservoir also includes a cap layer adjacent to the structured surface of the microstructured film.
A liquid dispenser according to the present invention includes a reservoir in which liquid can be stored within a plurality of elongated channels formed from overlaying layers of microstructured film. At least one layer of microstructured film has a dispensing edge, and at least one elongated channel has an outlet at the dispensing edge. The liquid dispenser also includes a transfer element in fluid communication with the dispensing edge of the reservoir that provides a location from which liquid stored in the reservoir can be controllably dispensed.
In one embodiment, a liquid dispenser of the present invention can be in the form of an ink jet cartridge comprising a housing having an opening and a reservoir located within the housing. The reservoir includes a plurality of elongated channels formed from overlaying layers of microstructured film. At least one layer has a dispensing edge, and at least one elongated channel has an outlet at the dispensing edge. Liquid (for example, ink) can be stored in the channels of the reservoir. The ink jet cartridge also includes a transfer element that is in fluid communication with the dispensing edge of the reservoir. The transfer element is located within the housing so that the transfer element is accessible through the opening so as to provide a location from which liquid stored in the reservoir can be controllably dispensed.
In another embodiment, a liquid dispenser of the present invention can be in the form of a writing instrument. The writing instrument comprises an elongated tubular housing having an opening at one end in which a reservoir is located. The reservoir includes a plurality of elongated channels formed from overlaying layers of microstructured film in which liquid (for example, ink) can be stored. At least one layer of microstructured film has a dispensing edge, and at least one elongated channel has an outlet at the dispensing edge. The reservoir is arranged within the elongated tubular housing so that the dispensing edge is accessible through the opening. Also, the writing instrument includes a nib that has a portion inserted into the end of the elongated tubular housing through the opening so that the nib is in fluid communication with the dispensing edge and so that liquid can be controllably dispensed from the reservoir through the nib.
Furthermore, the present invention relates to a liquid dispensing method. The liquid dispensing method includes providing a reservoir having a plurality of elongated channels formed from overlaying layers of microstructured film, storing liquid in the channels of the reservoir, and controllably dispensing the liquid stored in the channels of the reservoir.
Another method according to the present invention includes providing a reservoir that includes at least one layer of microstructured film having a plurality of elongated channels formed on a structured surface of the microstructured film, storing liquid in the channels of the reservoir, and removing liquid stored in the channels of the reservoir on demand.